Effects of asthma on cell components in peripheral blood among smokers and non-smokers

Clin Exp Allergy. 2003 Nov;33(11):1500-5. doi: 10.1046/j.1365-2222.2003.01730.x.


Background: Eosinophils play a central role in asthma, but the interplay of the effects of smoking, eosinophils and asthma remains unclear.

Objective: The primary objective of our study was to investigate the extent to which smoking modifies the effect of asthma on circulating eosinophils, CD4+ and CD8+ T cell counts.

Methods: Data were collected semiannually between 1987 and 1994 from HIV-negative participants in the Multicenter AIDS Cohort Study. Asthma was defined by a questionnaire at baseline as a self-report of diagnosed asthma. A total of 1420 blood samples from 197 asthmatics and 15 822 from 1997 non-asthmatics were collected.

Results: Eosinophil levels were higher in asthmatics (28% of asthmatics had eosinophils >/=4% and 16% of non-asthmatics) regardless of smoking history, but smoking modified the association between eosinophils and asthma. Namely, the odds ratios for eosinophils being >/=4% in asthmatics to non-asthmatics decreased from 2.7 (95% CI: 2.0, 3.6) in never, to 2.1 (1.4, 3.1) in former, and to 1.5 (0.9, 2.3) in current smokers. Cross-sectional and longitudinal analyses coherently showed that smoking increased eosinophils in non-asthmatics, but the converse was true for asthmatics. In contrast, no differences in peripheral blood T cell counts between asthmatics and non-asthmatics were observed.

Conclusion: Under the established link between increased eosinophils and asthma, these data indicate that smoking modified this relationship. This finding suggests that smoking plays a different immunological role in asthmatics and non-asthmatics.

Publication types

  • Multicenter Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Asthma / blood*
  • Asthma / immunology
  • CD4 Lymphocyte Count
  • CD4-CD8 Ratio
  • CD8-Positive T-Lymphocytes / immunology
  • Cohort Studies
  • Eosinophils / pathology
  • Humans
  • Leukocyte Count
  • Male
  • Middle Aged
  • Odds Ratio
  • Smoking / blood*
  • Smoking / immunology